diff --git a/pandas/core/indexes/category.py b/pandas/core/indexes/category.py
index 7f2860a963423..93df0d377c4fe 100644
--- a/pandas/core/indexes/category.py
+++ b/pandas/core/indexes/category.py
@@ -172,7 +172,10 @@ def _create_categorical(self, data, categories=None, ordered=None,
                 data = data.set_ordered(ordered)
             if isinstance(dtype, CategoricalDtype):
                 # we want to silently ignore dtype='category'
-                data = data._set_dtype(dtype)
+                if dtype != data.dtype:
+                    data = data._set_dtype(dtype)
+                else:
+                    data = data.copy()
         return data
 
     @classmethod